Driving Circuitry for Focused Ultrasound Noninvasive Surgery and Drug Delivery Applications

El‐Desouki, Munir M.; Hynynen, Kullervo

doi:10.3390/s110100539

Cited by 25 publications

(18 citation statements)

References 36 publications

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“…One method of measuring effective power is to use bidirectional power couplers [24], [42], [44], which consist of transformers attached to transmission lines. These couplers produce two voltage signals proportional to the forward and reflected power.…”

Section: Current Methodologiesmentioning

confidence: 99%

“…For ultrasound imaging systems, the focus of electronics research has largely been on improving computational power and element count [22]. However, for HIFU systems where the continuous power ratings must be significantly higher [23], the focus has been on reducing the cost, size and complexity [24], [25] whilst maintaining MRI compatibility [26], [27]. The exception is transcranial systems where the element count continues to increase due to improved steering capabilities [16], [28]- [30] When making thermally-formed lesions using HIFU, the total acoustic power is arguably the most critical value as it dictates the spatial-peak pulse-average intensity (I SPPA ) and spatial-peak temporal-average (I SP T A ), which both correlate with lesion volume (the latter being a better metric of heating for low duty cycle exposures [31]).…”

Section: Introductionmentioning

confidence: 99%

“…If underexposure occurs, the treatment may result in failure. Systems therefore must be calibrated so the acoustic power and thus intensity can be reliably controlled [24].…”

Section: Introductionmentioning

confidence: 99%

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HIFU Power Monitoring Using Combined Instantaneous Current and Voltage Measurement

Adams

McLaughlan

Carpenter

et al. 2020

IEEE Trans. Ultrason., Ferroelect., Freq. Contr.

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During HIFU therapy it is important that the electrical power delivered to the transducer is monitored to avoid under or over exposure, ensure patient safety and to protect the transducer itself. Due to ease of measurement, the transducer's potential difference may be as an indicator of power delivery. However, even when a transducer's complex impedance is well characterised at small amplitudes and matching networks are used, voltage-only (VO) monitoring cannot account for the presence of drive waveform distortion, changes to the acoustic path or damage to the transducer. In this study, combined current and voltage (CCV) is proposed as an MRIcompatible, miniature alternative to bi-directional power couplers that is compatible with switched amplifiers. For CCV power measurement, current probe data was multiplied by the voltage waveform and integrated in the frequency domain. Transducer efficiency was taken into account to predict acoustic power. The technique was validated with a radiation force balance (RFB). When using a typical HIFU transducer and amplifier, VO predictions and acoustic power had a maximum difference of 20%. However, under the same conditions, CCV only had a maximum difference of 5%. The technique was applied to several lesioning experiments and it was shown that when VO was used as a control between two amplifiers there was up to a 38% difference in lesion area. This greatly reduced to a maximum of 5% once CCV was used instead. These results demonstrate that CCV can accurately predict real-time electrical power delivery leading to safer HIFU treatments.

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Section: Current Methodologiesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

HIFU Power Monitoring Using Combined Instantaneous Current and Voltage Measurement

Adams

McLaughlan

Carpenter

et al. 2020

IEEE Trans. Ultrason., Ferroelect., Freq. Contr.

View full text Add to dashboard Cite

show abstract

“…Such systems provide the necessary amplitude and phase control whilst minimising harmonic distortion. However such systems are expensive, physically large [5], and suffer from poor electrical efficiency. This is especially problematic as the move towards multiple element transducers [6] to facilitate techniques such as beam steering and dynamic focus.…”

Section: Introductionmentioning

confidence: 99%

Gallium Nitride Based High-Power Switched HIFU Pulser with Real-Time Current/Voltage Monitoring

Carpenter

Cowell

Clegg

et al. 2019

2019 IEEE International Ultrasonics Symposium (IUS)

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High-Intensity Focussed Ultrasound (HIFU) techniques make use of ultrasound transducers capable of delivering high powers to be delivered at high frequencies. Real-time monitoring of power delivered can avoid damage to the transducer and injury to patients due to overexposure. This paper demonstrates the real-time current and voltage monitoring capabilities of a new Gallium-Nitride (GaN) based switched mode transmit pulser developed for the University of Leeds High-Intensity Focussed Ultrasound Array Research Platform (HIFUARP) system, which uses a novel approach of using an Analog Front End (AFE) floating on the transmitter output to provide high bandwidth current measurement.

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“…In transcranial therapy [4] they are of particular necessity to compensate skull's varying attenuation [5]- [7]. To achieve the electrical powers required for tissue ablation, therapeutic excitation circuits typically use class A amplifiers which are costly and inefficient [8]. As the element count of therapeutic systems increases, so does the physical size and cost.…”

Section: Introductionmentioning

confidence: 99%

A miniature HIFU excitation scheme to eliminate switching-induced grating lobes and nullify hard tissue attenuation

Adams

Cowell

Nie

et al. 2017

2017 IEEE International Ultrasonics Symposium (IUS)

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Abstract-Phased array transducers are increasingly prevalent in a therapeutic contex as they facilitate precise control of the beam intensity and focus. To produce enough acoustic energy for ablation, large and costly amplifiers are required. Miniaturised switched circuits provide an alternative that is both more cost effective and more efficient. However, the high Q factor and curved geometry of a therapeutic transducer lends itself to grating lobes that deposit energy in undesirable areas when driven with switched circuitry. In this work, harmonic reduction pulse with modulation (HRPWM) is applied to a simulation of a therapeutic array. An array was simulated along with a skull that varied in attenuation. A number of switching schemes were tested and where possible, their amplitude was adjusted to reduce pressure variation in the acoustic field after propagation through the skull. Of the switched schemes tested, HRPWM performed best; reducing harmonically induced grating lobes by 12 dB and limiting pressure field variance to 0.1 dB which increases intensity at the focal point and makes therapy more efficient.

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Driving Circuitry for Focused Ultrasound Noninvasive Surgery and Drug Delivery Applications

Cited by 25 publications

References 36 publications

HIFU Power Monitoring Using Combined Instantaneous Current and Voltage Measurement

HIFU Power Monitoring Using Combined Instantaneous Current and Voltage Measurement

Gallium Nitride Based High-Power Switched HIFU Pulser with Real-Time Current/Voltage Monitoring

A miniature HIFU excitation scheme to eliminate switching-induced grating lobes and nullify hard tissue attenuation

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